4.1 - Covalent Bonding
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covalent bond
electrostatic attraction between the nuclei of bonded atoms and a shared pair of electrons
covalent bond is formed
formed between atoms by the sharing of a pair of electrons
electrostatic attraction
The attraction between the shared pair of electrons and the nuclei of the atoms involved in a covalent bond
covalently bonded substances may be
simple molecular structures or giant covalent structures - Simple molecular structures –> oxygen and water - Giant covalent structures –> diamond and graphite
simple molecular structures have low melting and boiling points because
There are weak intermolecular forces between the molecules These forces require little energy to overcome
C60 is a simple molecular structure that
can not conduct electricity
as the relative molecular mass of a substance increases
the melting and boiling point will increase as well -> more electrons in the structure, so there are more intermolecular forces of attraction that need to be overcome -> larger amounts of heat energy are needed to overcome these forces, causing the compound to have a higher melting and boiling point
simple molecular structures are poor conductors of electricity (even when molten) because
• no free ions or electrons to move and carry the charge -> neutral charge • most covalent compounds do not conduct at all in the solid state • insulators
giant covalent structures
solids with high melting points, giant lattices
examples of giant covalent structures
diamond and graphite
all giant covalent structures have high melting points because
• strong covalent bonds between atoms • these require lots of energy to overcome
properties of diamond and use
diamond is very hard: - each carbon atom is covalently bonded to four other carbon atoms - the covalent bonds are very strong - tetrahedron shape (each atom bonded to four carbon atoms) the hardness of diamond makes it useful for cutting tools
Diamond has a high melting point because
a giant covalent structure - there are strong covalent bonds between atoms which need lots of energy to break
properties of graphite and use
• soft and slippery • each carbon atom is bonded to three other carbon atom forming layers • layers are free to slide over each other because there are only weak forces between the layers, not covalent bonds • graphite is used as pencil lead
graphite can conduct electricity and heat because
delocalised electrons are free to move
graphite has a high melting point because
• giant covalent structure • strong covalent bonds between atoms which need lots of energy to break
covalent compounds do not usually
conduct electricity
molecule
group of atoms joined by covalent bonds
why does lithium fluoride form ionic bonds
lithium gives one electron to fluoride (metal -> non-metal) - flouride gains one electron and hydrogen looses one
relative mass
(number x percent)+(number x percent) / 100
metals structure and bonding
giant metallic metallic -> high MP+BP
metals with non-metal structure and bonding
giant ionic ionic -> high MP+BP
group 4 structure and bonding
giant covalent covalent bonds -> high MP+BP
non-metals structure and bonding
simple molecular covalent bonds -> low MP+BP